In the building industry, the positioning of electrical outlet boxes and the connections thereto are covered by a number of building code requirements. In general, these code requirements are set up to insure a good workmanlike assembly of the outlet box in the builindg, and to insure safety in the use of electrical receptacle plugs in the outlet box and the permanent satisfactory positioning of power supply leads connecting to the box and outlet receptacles positioned therein.
Thus, in the assembly of the outlet boxes in walls, if these walls are made of non-combustible material, the boxes should be so installed that the front edge of the box will not set back of the finished surface more than 1/4 inch, whereas in walls and ceilings constructed of wood or other combustible materials, the outlet boxes shall be flush with the finished surface of or project from such wall premises (Article 370-10 Uniform Electrical Building Code). Yet other portions of the building code require that plaster surfaces that are broken or incomplete adjacent the box shall be repaired so that there are no gaps or open spaces at the edge of the outlet box.
Other portions of the building code require that where a fixture canopy or pan is used, any combustible wall or ceiling finish material exposed between the edge of the canopy or pan and the outlet box shall be covered with a non-combustible material (Article 370-15B), while Artilce 370-23 relates to non-metallic boxes. It requires that the supports or other mounting means for non-metallic boxes shall be outside of the box or the box shall be so constructed as to prevent contact between the conductors in the box and any metallic means in the box.
In many outlet boxes today, especially where they are provided in older buildings to replace prior installations, so-called Madison Holdites or other similar strap metal plates are used to secure the box to the wall, and these strap metal plates extend from outside the box to inside the box and provide auxiliary mounting means for the outlet box. But, the portions of the metallic members extending into the box from the outer surface thereof do provide a safety hazard, as well as a special problem in meeting the code requirements.
Reference is made to prior U.S. Pat. No. 3,115,265 on an expandable protector for an electrical outlet box, but such expandable protector involves a sleeve means made from a number of different metallic members that are costly and cumbersome to produce, assemble, and use. Furthermore, such expandable protector member does not provide any continuous flange means on a sleeve member connecting an outlet box to a supporting wall and to receptacle outlets positioned in the box. Hence, in prior installations, it was not assured that some part of the relatively short semi-randomly positioned flanges on the expandable protector would definitely bridge over holes in the wall and contact a wall surface. Nor did the prior unit positively aid in securing or supporting the duplex receptacle in the outlet box. The prior unit did not insure a positive permanent support of the duplex receptacle in the outlet assembly. Furthermore, the current tendency is that the requirements of the electrical building codes are becoming more stringent and the requirements for both grounding the outlet box itself and for providing a grounded conductor therein are being made stronger.
The general object of the present invention is to provide a novel and improved under plate for use in assembling duplex outlet receptacles in outlet boxes.
Another object of the invention is to provide a safer operative assembly of an outlet box, under plate and outlet receptacle.
Another object of the invention is to provide a relatively inexpensive, molded, one-piece plastic part to form an under plate in electrical outlet boxes, and to form this under plate, which only needs be formed in a minimum of different sizes for telescoping engagement with outlet boxes, and to provide a good connector medium and a safe insulation member connecting the outlet boxes to its cover plate and the duplex receptacle mounted in the outlet box.
The foregoing and other objects and advantages of the invention will be made more apparent as the specification proceeds.